linux-stable.git/include/linux/kernfs.h, branch v5.17.7

kernfs: Replace kernel.h with the necessary inclusions

2021-12-21T09:34:39+00:00

When kernel.h is used in the headers it adds a lot into dependency hell,
especially when there are circular dependencies are involved.

Replace kernel.h inclusion with the list of what is really being used.

Acked-by: Tejun Heo 
Signed-off-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20211209123008.3391-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

kernfs: switch global kernfs_rwsem lock to per-fs lock

2021-11-24T12:55:16+00:00

The kernfs implementation has big lock granularity(kernfs_rwsem) so
every kernfs-based(e.g., sysfs, cgroup) fs are able to compete the
lock. It makes trouble for some cases to wait the global lock
for a long time even though they are totally independent contexts
each other.

A general example is process A goes under direct reclaim with holding
the lock when it accessed the file in sysfs and process B is waiting
the lock with exclusive mode and then process C is waiting the lock
until process B could finish the job after it gets the lock from
process A.

This patch switches the global kernfs_rwsem to per-fs lock, which
put the rwsem into kernfs_root.

Suggested-by: Tejun Heo 
Acked-by: Tejun Heo 
Signed-off-by: Minchan Kim 
Link: https://lore.kernel.org/r/20211118230008.2679780-1-minchan@kernel.org
Signed-off-by: Greg Kroah-Hartman

kernfs: remove the unused lockdep_key field in struct kernfs_ops

2021-09-14T14:55:19+00:00

Not actually used anywhere.

Acked-by: Christian Brauner 
Acked-by: Tejun Heo 
Signed-off-by: Christoph Hellwig 
Link: https://lore.kernel.org/r/20210913054121.616001-4-hch@lst.de
Signed-off-by: Greg Kroah-Hartman

kernfs: remove kernfs_create_file and kernfs_create_file_ns

2021-09-14T14:54:55+00:00

All callers actually use __kernfs_create_file.

Acked-by: Christian Brauner 
Acked-by: Tejun Heo 
Signed-off-by: Christoph Hellwig 
Link: https://lore.kernel.org/r/20210913054121.616001-3-hch@lst.de
Signed-off-by: Greg Kroah-Hartman

kernfs: switch kernfs to use an rwsem

2021-07-27T07:29:15+00:00

The kernfs global lock restricts the ability to perform kernfs node
lookup operations in parallel during path walks.

Change the kernfs mutex to an rwsem so that, when opportunity arises,
node searches can be done in parallel with path walk lookups.

Reviewed-by: Miklos Szeredi 
Signed-off-by: Ian Kent 
Link: https://lore.kernel.org/r/162642770946.63632.2218304587223241374.stgit@web.messagingengine.com
Signed-off-by: Greg Kroah-Hartman

kernfs: add a revision to identify directory node changes

2021-07-27T07:29:14+00:00

Add a revision counter to kernfs directory nodes so it can be used
to detect if a directory node has changed during negative dentry
revalidation.

There's an assumption that sizeof(unsigned long) <= sizeof(pointer)
on all architectures and as far as I know that assumption holds.

So adding a revision counter to the struct kernfs_elem_dir variant of
the kernfs_node type union won't increase the size of the kernfs_node
struct. This is because struct kernfs_elem_dir is at least
sizeof(pointer) smaller than the largest union variant. It's tempting
to make the revision counter a u64 but that would increase the size of
kernfs_node on archs where sizeof(pointer) is smaller than the revision
counter.

Reviewed-by: Miklos Szeredi 
Signed-off-by: Ian Kent 
Link: https://lore.kernel.org/r/162642769895.63632.8356662784964509867.stgit@web.messagingengine.com
Signed-off-by: Greg Kroah-Hartman

kernfs: bring names in comments in line with code

2020-11-09T17:12:39+00:00

Fix two stragglers in the comments of the below rename operation.

Fixes: adc5e8b58f48 ("kernfs: drop s_ prefix from kernfs_node members")
Acked-by: Tejun Heo 
Signed-off-by: Willem de Bruijn 
Link: https://lore.kernel.org/r/20201015185726.1386868-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Greg Kroah-Hartman

kernfs: Add option to enable user xattrs

2020-03-16T19:53:47+00:00

User extended attributes are useful as metadata storage for kernfs
consumers like cgroups. Especially in the case of cgroups, it is useful
to have a central metadata store that multiple processes/services can
use to coordinate actions.

A concrete example is for userspace out of memory killers. We want to
let delegated cgroup subtree owners (running as non-root) to be able to
say "please avoid killing this cgroup". This is especially important for
desktop linux as delegated subtrees owners are less likely to run as
root.

This patch introduces a new flag, KERNFS_ROOT_SUPPORT_USER_XATTR, that
lets kernfs consumers enable user xattr support. An initial limit of 128
entries or 128KB -- whichever is hit first -- is placed per cgroup
because xattrs come from kernel memory and we don't want to let
unprivileged users accidentally eat up too much kernel memory.

Signed-off-by: Daniel Xu 
Acked-by: Chris Down 
Reviewed-by: Greg Kroah-Hartman 
Signed-off-by: Tejun Heo

kernfs: use 64bit inos if ino_t is 64bit

2019-11-12T16:18:04+00:00

Each kernfs_node is identified with a 64bit ID.  The low 32bit is
exposed as ino and the high gen.  While this already allows using inos
as keys by looking up with wildcard generation number of 0, it's
adding unnecessary complications for 64bit ino archs which can
directly use kernfs_node IDs as inos to uniquely identify each cgroup
instance.

This patch exposes IDs directly as inos on 64bit ino archs.  The
conversion is mostly straight-forward.

* 32bit ino archs behave the same as before.  64bit ino archs now use
  the whole 64bit ID as ino and the generation number is fixed at 1.

* 64bit inos still use the same idr allocator which gurantees that the
  lower 32bits identify the current live instance uniquely and the
  high 32bits are incremented whenever the low bits wrap.  As the
  upper 32bits are no longer used as gen and we don't wanna start ino
  allocation with 33rd bit set, the initial value for highbits
  allocation is changed to 0 on 64bit ino archs.

* blktrace exposes two 32bit numbers - (INO,GEN) pair - to identify
  the issuing cgroup.  Userland builds FILEID_INO32_GEN fids from
  these numbers to look up the cgroups.  To remain compatible with the
  behavior, always output (LOW32,HIGH32) which will be constructed
  back to the original 64bit ID by __kernfs_fh_to_dentry().

Signed-off-by: Tejun Heo 
Reviewed-by: Greg Kroah-Hartman 
Cc: Namhyung Kim

kernfs: combine ino/id lookup functions into kernfs_find_and_get_node_by_id()

2019-11-12T16:18:04+00:00

kernfs_find_and_get_node_by_ino() looks the kernfs_node matching the
specified ino.  On top of that, kernfs_get_node_by_id() and
kernfs_fh_get_inode() implement full ID matching by testing the rest
of ID.

On surface, confusingly, the two are slightly different in that the
latter uses 0 gen as wildcard while the former doesn't - does it mean
that the latter can't uniquely identify inodes w/ 0 gen?  In practice,
this is a distinction without a difference because generation number
starts at 1.  There are no actual IDs with 0 gen, so it can always
safely used as wildcard.

Let's simplify the code by renaming kernfs_find_and_get_node_by_ino()
to kernfs_find_and_get_node_by_id(), moving all lookup logics into it,
and removing now unnecessary kernfs_get_node_by_id().

Signed-off-by: Tejun Heo 
Reviewed-by: Greg Kroah-Hartman